Champion and Nearby Fields

The Champion field is a complex oil and gas field, situated 40 kilometres
north-northwest of Bandar Seri Begawan, in water depths of 10 to 45 metres
(Figures 5.51 and 5.52).
The shallows in the area are covered with coral reef patches. The field
was discovered in 1970 by Champion-1, drilled in its northern part.

The first platform was completed
in 1972, to produce from shallow, oil-bearing intervals. A major appraisal
drilling campaign followed in 1972 - 1973. At the same time, a field development
plan was formulated, with 6 additional in-line platforms. In 1974, a blow-out
at Champion-41 caused a delay of the appraisal / development operations.
During 1975 - 1976, eight isolated appraisal wells were drilled to compensate
for this delay. These wells not only aided in further delineating the main
field, but also discovered hydrocarbons beyond the reach of the primary
development platforms, namely the separate Champion West structure, to
the northwest of the main field, and the very shallow accumulations to
the southeast (Champion Southeast). Another blow-out occurred in the northern
part of the Champion Main field in well CP-141,
in early 1979.

During the early development stages of the field, the extreme complexity,
of structure as well as reservoir architecture, was recognised. In 1978,
a grid concept for platform location was introduced for the shallow part
of the main field, which contains the bulk of the known oil reserves. This
decision facilitated the long term engineering planning, and ensured that
most of the future draining / injection points are within easy reach of
a platform location.

Construction of the centralised field facilities at Champion-7
began in 1980 and was completed in 1983.

To date (1/1/96)
282 wells have been drilled, of which 118 are producing. Average production
rates over 1995 were 10,000 m3/d of liquids and 1.2 million
m3/d of gas (including production from Champion Southeast).
Some 7,000 m3/d of water is injected in order to support the
pressure in a number of reservoirs.

The Champion field is highly compartmentalised, characterised by large
areas of fault / dip closures, from the seabed downwards. Combined with
the multilayered nature of the stratigraphic succession, striking sub-parallel
to most of the faults, the numerous hydrocarbon traps are relatively small
and generally stacked. Block widths range from 100- 450 metres.

To the north-west of the main anticline, the deep, smaller, early rollover
structure is termed Champion
West. To the south-east, hydrocarbons are found trapped in fault slivers
parallel to the main growth fault and this set of accumulations is termed
Champion Southeast.
The Peragam gas field
is directly below the Champion field

Hydrocarbon migration was almost certainly
from the west, filling traps on the westerly flank of the structure with
the prospective sequence extending almost from seabed to below 3,000 metres.
Salient features of the hydrocarbon distribution are:

In the Shallow and Very Shallow levels, the more easterly accumulations
have shallower hydrocarbon water contacts (Figure 5.52).

The major accumulations in shallower reservoirs occur further eastward
than deeper ones, since faulting cuts progressively younger sediments in
an easterly direction (Figure 5.52).

The hydrocarbon distribution broadly follows the shift in crestal position
with depth so that accumulations at less than 900 metres are restricted
to the southeast while those deeper than 1,200 metres occur predominantly
in the north (Figure 5.52).

The bulk of the Champion oil reserves are contained in the very shallow
and shallow intervals of the Main field, At present, there are more than
900 identified oil and gas reservoirs. Most of these reservoirs are small,
with 88% having a STOllP of less than 1.0 million m3.

The expected ultimate recovery for the Champion field
is 128 million m3 of oil (27 % recovery), 2.18 million
m3 of condensate (34% recovery) and 27.7 109
m3 of gas (55% recovery).

Original reservoir pressures are at
or near hydrostatic in the very shallow and shallow intervals. Significant
over-pressures are first encountered in the intermediate intervals and
gradually increase to more than 22,750 kPa (3,300 psi) above hydrostatic
in the deep intervals, at about 2,900 metres subsea.

On production, reservoir pressures
are observed to drop rapidly. The numerous fault barriers, the absence
of large gas caps, and low initial gas-oil ratios, result in generally
low natural drive energy. Solution gas is an important drive mechanism.
Thus, primary recovery efficiencies are to some extent related to gas/oil
ratios, and, less importantly, abandonment pressure policies.

The crestal reservoirs are, in general, more shielded from aquifer drive
than those on the flanks and the isolated reservoirs are, in principle,
targets for supplementary recovery.

The highly permeable reservoirs in the field are considered favourable
for water injection. The relatively low oil viscosity (3 cp) for this heavy
(22° API or 920 kg/m3) oil together with the small relative
permeability for water (around 0.2) results in a not too unfavourable mobility
ratio of about 1.5. However, the significant vertical and lateral permeability
heterogeneities may lead to some reduction in sweep efficiency. Another
complication is the limited confinement of target reservoirs, caused by
the limited sealing capacity of the surrounding faults.

The gas in the Champion field has a CO2
content that varies from less than 1 % to more than 80%. CO2
is highest in the very shallow and shallow reservoirs and decreases with
depth. CO2 in Champion is therefore probably related to the
biodegradation
of hydrocarbons .